System and driving method for light emitting device display

• US 10,555,398 B2
• Filed: 11/30/2017
• Issued: 02/04/2020
• Est. Priority Date: 04/18/2008
• Status: Active Grant

• Current Assignee: IGNIS Innovation Incorporated
• Original Assignee: IGNIS Innovation Incorporated
• Inventors: Nathan, Arokia, Chaji, Gholamreza, Alexander, Stefan
• Primary Examiner(s): Nguyen, Kevin M
• Application Number:
  US15/827,015
• Publication Number:
  US 20180084621A1
• Time in Patent Office: 796 Days
• CPC Class Codes: G09G 2300/043 Compensation electrodes or other additional electrodes in matrix displays related to distortions or compensation signals, e.g. for modifying TFT threshold voltage in column driver
• CPC Class Codes: G09G 2300/0819 used for counteracting undesired variations, e.g. feedback or autozeroing
• CPC Class Codes: G09G 2300/0852 being a dynamic memory with more than one capacitor
• CPC Class Codes: G09G 2300/0861 with additional control of the display period without amending the charge stored in a pixel memory, e.g. by means of additional select electrodes
• CPC Class Codes: G09G 2310/0262 The addressing of the pixel, in a display other than an active matrix LCD, involving the control of two or more scan electrodes or two or more data electrodes, e.g. pixel voltage dependent on signals of two data electrodes
• CPC Class Codes: G09G 2320/0252 Improving the response speed
• CPC Class Codes: G09G 2320/043 Preventing or counteracting the effects of ageing
• CPC Class Codes: G09G 2320/045 Compensation of drifts in the characteristics of light emitting or modulating elements
• CPC Class Codes: G09G 3/3233 with pixel circuitry controlling the current through the light-emitting element
• CPC Class Codes: G09G 3/3241 the current through the light-emitting element being set using a data current provided by the data driver, e.g. by using a two-transistor current mirror
• CPC Class Codes: G09G 3/3258 with pixel circuitry controlling the voltage across the light-emitting element
• CPC Class Codes: G09G 3/3283 in which the data driver supplies a variable data current for setting the current through, or the voltage across, the light-emitting elements
• CPC Class Codes: G09G 3/3291 in which the data driver supplies a variable data voltage for setting the current through, or the voltage across, the light-emitting elements
• CPC Class Codes: H05B 45/48 having LEDs organised in strings and incorporating parallel shunting devices
• CPC Class Codes: H05B 45/60 Circuit arrangements for operating LEDs comprising organic material, e.g. for operating organic light-emitting diodes [OLED] or polymer light-emitting diodes [PLED]

Abstract

A light emitting device display, its pixel circuit and its driving technique is provided. The pixel includes a light emitting device and a plurality of transistors. A bias current and programming voltage data are provided to the pixel circuit in accordance with a driving scheme so that the current through the driving transistor to the light emitting device is adjusted.

Claims

1. A display system comprising:

a pixel array having a plurality of pixel circuits, each of the plurality of pixel circuits being configured to be operated in a programming cycle, during which each pixel circuit receives a programming voltage according to display data, and operated in a driving cycle different from the programming cycle, during which each pixel emits light according to the programming voltage, each pixel circuit comprising;

a light emitting device;

a capacitor having a first and a second terminal, the first terminal of the capacitor coupled to a signal line;

a first switch transistor having a gate terminal, a first terminal, and a second terminal, the gate terminal of the first switch transistor coupled to a select line, the first terminal of the first switch transistor coupled to the second terminal of the capacitor, the second terminal of the first switch transistor coupled to the light emitting device;

a second switch transistor having a gate terminal, a first terminal, and a second terminal, the gate terminal of the second switch transistor coupled to a select line, the first terminal of the second switch transistor coupled to the light-emitting device, the second terminal of the second switch transistor coupled to a bias line; and

a driving transistor for driving the light emitting device, the driving transistor having a gate coupled to the second terminal of the capacitor; and

driver circuitry for programming the pixel circuit during the programming cycle and driving the pixel circuit during a driving cycle, the driver circuitry providing programming voltages on the signal line as a function of the display data for the pixel circuit, and providing a controllable bias current, independent of programming data for the pixel circuit, on the bias line to compensate for spatial and temporal non-uniformities of the pixel circuits.

2. The display system according to claim 1, wherein for each pixel circuit, the gate terminal of the first switch transistor and the gate terminal of the second switch transistor are operated by a single select line.

3. The display system according to claim 1, wherein for each pixel circuit, the second switch transistor includes a first terminal coupled to the bias line and a second terminal coupled to a connection node between the light emitting device and the driving transistor.

4. The display system according to claim 1, wherein the display data includes a plurality of voltage signals for dividing current in different current levels for different grey scales.

5. The display system according to claim 1, wherein each light emitting device includes an organic light emitting diode.

6. The display system according to claim 1, wherein at least one of the transistors of each pixel circuit is a thin film transistor.

7. The display system according to claim 1, wherein each transistor is implemented using poly silicon, nano/micro (crystalline) silicon, amorphous silicon, CMOS, organic semiconductor, metal organic technologies, or a combination thereof.

8. The display system according to claim 1, wherein the pixel array includes an active matrix array.

9. The display system according to claim 1, wherein the controllable bias current is a predetermined fixed current.

10. The display system of claim 1, further comprising a controllable current source for providing said controllable bias current, wherein the controllable current source comprises a calibrated current mirror for operating on the bias line based on a reference current.

11. The display system of claim 1, further comprising a controllable current source for providing said controllable bias current, wherein the controllable current source comprises a voltage to current converter for converting voltage to the bias current.

12. The display system of claim 1, further comprising a controllable current source for providing said controllable bias current, wherein the controllable current source is calibrated via a data stored in a memory.